package org.apache.lucene.search.spans;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.IOException;

import java.util.Collection;
import java.util.Set;

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.Query;
import org.apache.lucene.util.ToStringUtils;

/** Matches spans near the beginning of a field. */
public class SpanFirstQuery extends SpanQuery {
	private SpanQuery match;
	private int end;

	/**
	 * Construct a SpanFirstQuery matching spans in <code>match</code> whose
	 * end position is less than or equal to <code>end</code>.
	 */
	public SpanFirstQuery(SpanQuery match, int end) {
		this.match = match;
		this.end = end;
	}

	/** Return the SpanQuery whose matches are filtered. */
	public SpanQuery getMatch() {
		return match;
	}

	/** Return the maximum end position permitted in a match. */
	public int getEnd() {
		return end;
	}

	public String getField() {
		return match.getField();
	}

	/**
	 * Returns a collection of all terms matched by this query.
	 * 
	 * @deprecated use extractTerms instead
	 * @see #extractTerms(Set)
	 */
	public Collection getTerms() {
		return match.getTerms();
	}

	public String toString(String field) {
		StringBuffer buffer = new StringBuffer();
		buffer.append("spanFirst(");
		buffer.append(match.toString(field));
		buffer.append(", ");
		buffer.append(end);
		buffer.append(")");
		buffer.append(ToStringUtils.boost(getBoost()));
		return buffer.toString();
	}

	public void extractTerms(Set terms) {
		match.extractTerms(terms);
	}

	public Spans getSpans(final IndexReader reader) throws IOException {
		return new Spans() {
			private Spans spans = match.getSpans(reader);

			public boolean next() throws IOException {
				while (spans.next()) { // scan to next match
					if (end() <= end)
						return true;
				}
				return false;
			}

			public boolean skipTo(int target) throws IOException {
				if (!spans.skipTo(target))
					return false;

				if (spans.end() <= end) // there is a match
					return true;

				return next(); // scan to next match
			}

			public int doc() {
				return spans.doc();
			}

			public int start() {
				return spans.start();
			}

			public int end() {
				return spans.end();
			}

			public String toString() {
				return "spans(" + SpanFirstQuery.this.toString() + ")";
			}

		};
	}

	public Query rewrite(IndexReader reader) throws IOException {
		SpanFirstQuery clone = null;

		SpanQuery rewritten = (SpanQuery) match.rewrite(reader);
		if (rewritten != match) {
			clone = (SpanFirstQuery) this.clone();
			clone.match = rewritten;
		}

		if (clone != null) {
			return clone; // some clauses rewrote
		} else {
			return this; // no clauses rewrote
		}
	}

	public boolean equals(Object o) {
		if (this == o)
			return true;
		if (!(o instanceof SpanFirstQuery))
			return false;

		SpanFirstQuery other = (SpanFirstQuery) o;
		return this.end == other.end && this.match.equals(other.match)
				&& this.getBoost() == other.getBoost();
	}

	public int hashCode() {
		int h = match.hashCode();
		h ^= (h << 8) | (h >>> 25); // reversible
		h ^= Float.floatToRawIntBits(getBoost()) ^ end;
		return h;
	}

}
